Allosuckling in cattle: Gain or compensation?

Abstract

The objective of this study was to assess the impact of allosuckling on the growth of calves in a herd of domestic cattle. We determined (i) if allosucking calves achieved a better weight gain than non-allosucking calves ingesting milk surplus to maternal milk supply or if they were compensating for growth and/or nutritional deficiency, and (ii) if the growth and development of the calf is affected by allonursing behaviour of its dam. If a compensatory function of the behaviour was valid, then calves should compensate for a lower birth body mass and/or maternal nutrient insufficiencies (‘maternal sucking rate’, i.e. a low frequency of acceptance of the calf's sucking attempts by its mother) through allosuckling. Observations were made in a socially stable group of 21 lactating cows and their 18 calves (7 males and 11 females) from birth until 203 days of the calf's life. During 289 h of observation 389 sucking attempts and 1404 suckling bouts were recorded, 27% of sucking attempts and 19% of suckling bouts being non-filial. All allosucking calves sucked their mothers frequently. Thus, allosuking in calves did not mean a complete failure of maternal care provided to filial calves. The calves that allosucked most frequently tended to grow less intensively (growth gain calculated from birth and weaning weights) and tended to reach a lower weaning weight than calves sucking non-maternal dams with lower frequency (GLM, F (1,17) = 3.23, P = 0.063, F (1,17) = 4.75, P = 0.046, respectively). Growth gain or weaning weight of the filial calves was not affected by allonursing frequency of the mother ( P = 0.66, P = 0.66, respectively). A higher incidence of allosucking was predicted in calves with lower birth weight (GEE, χ ( 1 ) 2 = 3.73 , P = 0.05), and in calves with lower maternal sucking rate ( χ ( 1 ) 2 = 3.99 , P = 0.05). Moreover, birth weight and maternal sucking rate influenced allosucking frequency interactively ( χ ( 1 ) 2 = 4.45 , P < 0.05). In conclusion, the cattle calves that frequently sucked non-maternal dams were most likely compensating for some deficiency, such as low birth weight and/or insufficient supply of maternal milk. This behaviour did not have a negative effect on the growth of progeny of the allonursing dams. Our results supported the hypothesis that allosuckling could be a behaviour through which the calves compensate for low birth weight and/or nutritional deficiency.